Tooth filling materials Dental amalgams & alternative materials

Context - Amalgam is a combination of mercury with other metals and has been used as a tooth
filling material since early in the 19th century.

Alternative tooth-coloured materials are increasingly used because they look better
and require less intervention.

How safe are different tooth filling materials? Are they equally effective in ensuring
dental health?

An assessment by the European Commission Scientific Committees on Emerging and Newly Identified Health Risks (SCENIHR) and on Health and Environmental Risks (SCHER).

The answers to these questions are a faithful summary of two opinions produced in 2008 by scientific committees of the European Commission: "The safety of dental amalgam and alternative dental restoration materials for patients and users" by SCENIHR (Scientific Committee on Emerging and Newly Identified Health Risks) and “The environmental risks and indirect health effects of mercury in dental amalgam" by SCHER (Scientific Committee on Health and Environmental Risks). Learn more...

1. Introduction

Amalgam fillings

Dental amalgam is a combination
of mercury with other metals and
has been used for over 150 years for the treatment of
tooth cavities because it is very
strong and durable. Moreover, it is soft enough to adapt to the size and
shape of the tooth cavity, yet
hardens sufficiently fast to make it practical. However, concerns have
been voiced about possible harmful effects of the mercury present in
dental amalgams.

Though it may still be considered a material of choice for some
fillings in the back teeth, the use of
amalgams has been decreasing in
recent years, because it is not tooth-coloured and does not adhere to
the surface of the tooth.

Alternative tooth-coloured filling materials have become increasingly
popular. Not only do these materials look better, but they require the
dentist to remove less tooth material. In addition they do not contain
mercury. As a result, the teaching
of the use of amalgams has either
been reduced or discontinued in many dental schools in Europe in favour
of alternative materials.
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2. How are dental amalgams made?

Mercury is a
heavy metal, sometimes known as
quicksilver, that occurs naturally in the environment in different
chemical forms. The pure form,
elemental mercury, is liquid at
room temperature and slowly forms a vapour in the air.

Dental amalgams are made by
mixing one part of liquid mercury
with one part of a mixture of other metals: mainly silver, but also tin,
some copper and small amounts of zinc. The setting
amalgam has the consistency of a
paste and is pressed firmly into the prepared
tooth cavity to make the filling as
strong as possible. During this process, some excess mercury rises to
the surface and is removed by the dentist. The amalgam becomes solid
quickly and gradually hardens over a few hours to form a strong
restoration that could last many years.

Set amalgam restorations release
mercury vapour but much less so
than liquid mercury. Amalgams
corrode over time very slowly, which may contribute to overall exposure
of the patient to mercury, but the exact level of this is not known.
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3. How can dental patients and workers be exposed to mercury from amalgams?

The general public is for instance exposed to
mercury when eating contaminated
fish, using cosmetics, medicinal products and medical devices that
contain mercury – including
dental amalgams – or at certain
workplaces where mercury is used
(see question 8).

The main exposure of patients to
mercury from
dental amalgam happens when they
are having fillings placed or removed.

To reduce exposure to mercury of
dental patients, it is better to leave
amalgam fillings in place unless
there is a medical reason to remove them. However, it may be advisable
to remove fillings in patients who are suspected to have allergic
reactions to one of the metals in the amalgam.

While amalgam fillings are in
place, patients are exposed to
mercury that is released through
normal wear, but the exposure is much lower than during placement and
removal.

Dental workers are considerably more exposed to
mercury than the general
population. Their main sources of exposure are vapours released when
placing or removing fillings and the exhaust air from dental vacuum
systems. However, dental workers today are exposed to much less mercury
than in the past because of improvements in technique and in hygiene
measures, and because of the steady decline in the use of
amalgams.
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4. What health effects could be linked to the form of mercury contained in dental amalgams?

4.1
People are mainly exposed to
elemental mercury by breathing in
its vapour, since contact with the skin or
ingestion leads to very little
absorption into the body. Mercury
vapour is absorbed in the lungs,
spreads to the entire body and is then slowly excreted.

Breathing in extremely high concentrations of
mercury may produce
bronchitis and
pneumonia and affect the
central system, for instance
leading to muscle tremors. Long-term exposure to high levels may affect
the kidneys and the inside of the mouth and gums. Such effects have been
observed in some workers employed in industries using mercury.

However, the amount released by
dental amalgams is much lower than
the limits allowed for exposure at work. There is no evidence that the
other metallic elements in
amalgams present a health risk,
apart from allergic reactions.
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4.2 Dental amalgam fillings
occasionally cause local effects in the mouth, such as allergic
reactions of the gums and of the skin inside the mouth, but this happens
only rarely and is normally easy to manage. There have been claims that
dental amalgam fillings might harm
the kidneys or have effects on the
nervous system or the mind. But
studies on human populations have not found such link.

It is concluded that the current use of
dental amalgams does not pose a
health risk beyond occasional local effects.
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5. What are the possible health effects of alternative tooth filling materials?

5.1
In modern dentistry, restorations are increasingly made with
alternative, tooth-coloured materials. They vary in composition and
properties and include composites,
cements, and sealants. Composites,
for instance, contain many components, including a resin base and a
ceramic filler. Composites are applied as a paste to the
tooth cavity and typically hardened
using visible blue light.

Some of the alternative materials are chemically very complex and not
necessarily without any health effects. The substances within the
material react inside the tooth and with the surrounding
soft tissue. In the laboratory, it
has been shown that certain resins that could remain present in the
filling material can affect gum and pulpcells and cause
mutations although this may not
have any medical significance.
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5.2
Certain resins used in alternative materials can, in rare cases, lead
to allergic reactions in patients or dental workers. The light used to
harden resins seems to be safe for most patients and users, when applied
properly, but can occasionally cause adverse reactions.

Alternative materials have now been in medical use for more than
thirty years with little evidence of adverse health effects. Over that
time the materials themselves have been modified, improved and made less
harmful. However, their full chemical composition is rarely disclosed
and is hard to determine, and information on exposure is scarce and
difficult to obtain. Therefore, it may not be possible to confirm on the
basis of scientific evidence that all alternative tooth filling
materials are safe.
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6. Conclusion on health effects of dental amalgams and their alternatives on users

6.1
Both dental amalgams and various
alternative materials are considered effective and safe to use. They are
associated with a very small proportion of local effects in the mouth
and there is no evidence that they can cause disease. The relative risks
and benefits of using different tooth filling materials should be
explained to patients and the public at large.
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6.2 Dental amalgam fillings can, in
rare cases, cause local allergic reactions and related conditions.
However, current evidence does not support any link between
dental amalgams and diseases –
neither diseases of the urinary,
neurological, reproductive and
immune systems nor any psychological conditions.

Amalgam is a safe material to use
for dental restorations. As with any other medical intervention, caution
should be exercised when considering the placement of tooth fillings in
pregnant women. Mercury exposure
may be higher among dental personnel than in the general population, but
there are very few reports of any adverse effects for that particular
group.
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6.3
Some components used in the preparation of alternative tooth filling
materials can cause local allergic reactions, both in patients and in
dental workers, although the number of cases is very low. There is no
evidence of any link between the use of alternative tooth filling
materials and any neurological or
other health disorders. However, data are sparse and caution should be
exercised before introducing new variations of these materials into the
market.
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7. What is the environmental risk of the use of dental amalgams and alternative materials?

7.1 Mercury occurs naturally in the
environment in different chemical forms.
Elemental mercury is the form used
in dental amalgams. Forms more
commonly found in nature are
inorganic mercury and
organic mercury. Natural events
(e.g. weathering of rocks) and human activities (e.g. fuel and waste
combustion and, to a lesser extent, use and disposal of dental amalgams)
can cause releases of these different forms of mercury into the
environment.

Wastewater released by dental clinics could increase the concentration
of inorganic mercury in water
bodies. The added risk for aquatic organisms of this source of inorganic
mercury is considered low. Sludge from plants that treat such wastewater
present a low risk for soil-dwelling organisms. In addition, the
cremation of individuals with
dental amalgam fillings also leads
to releases into air and deposition on soil.

The main environmental concern relates to
methylmercury, an
organic form of mercury, because it
can accumulate in organisms. The
levels of methylmercury increase along the
food chain and with age. Some of
the mercury released by the use of
dental amalgams will be converted
into methylmercury. Though estimates are available of the amounts of
mercury released by the use and disposal of dental amalgams in the
European Union, it is not possible to say what proportion of the risk
associated with organic mercury
present in the environment is due to releases from amalgams.
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7.2
For alternative tooth filling materials, potential effects on animals
are known for certain components. However, available information is too
limited to assess the environmental risk and compare it to
dental amalgams.
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8. How serious are the risks of indirect exposure to mercury from disposal dental amalgams?

Mercury present in the
environment – including that released by the use and disposal of
dental amalgams – can be taken up
by the humans through air, water and food. The general public is mainly
exposed to methylmercury through
the diet (particularly fish), and to
elemental mercury vapours at
certain workplaces and from tooth fillings. Methylmercury is
particularly poisonous to the
nervous system.

9. What further information is needed on environmental risks of dental amalgams?

To enable a full assessment of environmental risks, more information
is needed on regional variations across the EU in the use of
dental amalgam as well as the
related release and fate of
mercury, including emissions from
crematoria. It is also necessary to compile data on the effects of
different forms of mercury on humans and on the environment as well as a
review of the way methylmercuryaccumulates in organisms under
different EU conditions. The relative contribution of dental mercury to
the overall mercury pool in the environment needs to be determined.
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